My experience of London:
- There's little difference, time-wise, between being located in a town on commuter rail, vs somewhere three connections away on the tube. If you're inside the M25 but outside the North / South Circular, you need to be very close to a station or you're practically worse off than someone living in a town on the railway.
- Motorcycles and scooters, and increasingly, electric bicycles, are the big hack. Free or cheap parking, mostly unaffected by traffic (filtering), not stuck when the trains are cancelled, not constrained by the sparseness of the rail and tube network as you get further from the centre.
Crossrail isn't open yet (due next year, but I wouldn't bet on it); Crossrail 2 is mothballed and probably won't be built for a few decades.
I live in a 120sqm 4 bed house with garden in Enfield, 40 minutes motorcycle commute from Clerkenwell, or 60-80 minutes by tube and train, depending on delays and timing (don't leave enough slack and you miss a connection). We used to live in a very small 60 sqm 3 bed house with garden in Bow, which was about 30 minutes from Clerkenwell. Mortgage now is £1500; rent (for over 10 years, nice landlord) used to be £1300. There's fewer food delivery options, and an Uber home is (or was) the preferred route after a night out, vs a night bus to Bow, but overall it's a higher quality of life.
Of course, with Brexit, I'm headed for Zurich.